There have been considerable efforts on the part of mobile operators to find ways to offload data traffic from their cellular networks to wireless local area networks (“WLANs”). One of the challenges in doing so involves carrying such a transfer during an active data session. For example, while both the WLAN and the cellular interfaces are active for data communication in a device, if the Internet protocol (“IP”) routing rules on a wireless device change during a YOUTUBE® video streaming session over WLAN such that the YOUTUBE® traffic is re-routed to the cellular interface, then the video playback stops. After re-routing, the device continues receiving video content over WLAN but sends transport control protocol (“TCP”) acknowledge messages (“ACKs”) over the cellular interface, which are dropped by the remote YOUTUBE® host. Once the TCP send window closes, the remote host stops sending data to the device. The YOUTUBE® client is not aware of the re-routing and does not take any measures to avoid this. From its point of view, it sent duplicate ACKs to the remote host but suddenly stopped receiving new data.
In short, when the IP-routing rules in a wireless device redirect an application's traffic to a different IP interface, while the previously used IP interface remains active in the wireless device, the application does not detect this change and does not react to avoid the communication interruption. This poses challenges to efforts to offload cellular traffic to WLAN networks.